God spoke to Moshe after the death of two of Aharon’s sons (detailed in parashat Shemini). Moshe was told to warn Aharon, the Kohen Gadol, not to enter the Holy of Holies (Kodesh Hakodashim) area of the Mishkan (Tabernacle), except on Yom Kippur. The sidrah details the Yom Kippur service in the Mishkan: Aharon is to wear his tunic, breeches, sash and turban. The people will provide two male goats. Aharon will have to bring a bull as a chatat (sin) offering and a ram as an olah (elevation) offering. He must place lots on the two goats, designating one to be a chatat and the other to be thrown off a cliff in the wilderness. Inside the Kodesh Hakodashim, he will bring an incense offering (ketoret).
Before sending away the goat to the wilderness, Aharon is to lean his two hands upon its head and confess the transgressions of the nation.
The sin-offering bull and the remaining goat are removed to outside the camp, where their flesh is burned. The nation was commanded to fast on Yom Kippur. When Yom Kippur arrived, Aharon did exactly as commanded by God. This special service was to be repeated every year by future Kohen Gadols.
It is forbidden to bring an animal offering to anywhere other than the Mishkan. Neglecting this results in a severe punishment.
It is forbidden to consume the blood of any animal. After doing shechita (slaughter) on kosher fowl or non-domesticated animals, there is a mitzvah to cover the blood. A bird that was not killed in the prescribed fashion emits ritual impurity to one who eats it (tumah).
The laws of forbidden relationships are listed, such as with close relatives, or with another’s spouse. Adhering to the laws about forbidden relationships is a critical factor in the nation’s well-being in its Land.